﻿288 
  REPORT 
  UNITED 
  STATES 
  ENTOMOLOGICAL 
  COMMISSION. 
  

  

  which 
  lie 
  to 
  the 
  eastward 
  separating 
  it 
  from 
  the 
  valley 
  of 
  the 
  Blackfoot. 
  

   This 
  upper 
  valley, 
  after 
  being 
  abandoned 
  by 
  the 
  stream, 
  continues 
  

   on 
  southwaid 
  to 
  the 
  Bear, 
  where 
  it 
  is 
  known 
  as 
  Gentile 
  Valley, 
  and 
  of 
  

   which 
  we 
  have 
  spoken 
  above. 
  

  

  Passing 
  through 
  the 
  Portneuf 
  Eange, 
  the 
  Portneuf 
  enters, 
  near 
  its 
  

   lower 
  end, 
  a 
  broad, 
  fine 
  valley, 
  occupied 
  by 
  Marsh 
  Creek, 
  the 
  most 
  im- 
  

   portant 
  tributary 
  of 
  the 
  river. 
  This 
  valley 
  heads 
  opposite 
  that 
  of 
  the 
  

   Malade, 
  and 
  extends, 
  with 
  a 
  gradually 
  decreasing 
  width, 
  28 
  miles 
  north- 
  

   ward. 
  Its 
  greatest 
  width 
  is 
  12 
  miles. 
  Bench 
  land 
  forms 
  the 
  greater 
  

   part 
  of 
  the 
  valley, 
  and 
  this 
  produces 
  mainly 
  sage, 
  with 
  a 
  small 
  admix- 
  

   ture 
  of 
  grass. 
  Marsh 
  Creek, 
  the 
  small 
  stream 
  which 
  flows 
  through 
  this 
  

   valley, 
  has 
  a 
  marshy 
  bottom 
  land 
  through 
  most 
  of 
  its 
  course, 
  from 
  one- 
  

   fourth 
  of 
  a 
  mile 
  to 
  a 
  mile 
  in 
  breadth, 
  which 
  produces 
  marsh 
  grasses 
  and 
  

   willows. 
  All 
  the 
  valley 
  can 
  be 
  burned 
  over, 
  as 
  well 
  as 
  the 
  lower 
  slopes 
  

   of 
  the 
  Portneuf 
  Eange 
  on 
  the 
  east 
  and 
  of 
  the 
  Bannack 
  Eange 
  on 
  

   the 
  west. 
  These 
  ranges 
  contain 
  but 
  little 
  timber, 
  and 
  that 
  near 
  their 
  

   crests. 
  

  

  West 
  of 
  the 
  Bannack 
  Eange 
  are 
  the 
  valleys 
  of 
  the 
  upper 
  waters 
  of 
  the 
  

   Little 
  Malade 
  and 
  of 
  Bannack 
  Creek, 
  both 
  open 
  and 
  grassy, 
  with 
  more 
  

   or 
  less 
  sage, 
  and 
  both 
  easily 
  burnable. 
  

  

  At 
  the 
  foot 
  of 
  Marsh 
  Creek 
  Valley 
  the 
  Portneuf 
  turns 
  to 
  the 
  west 
  for 
  

   a 
  few 
  miles, 
  cutting 
  its 
  way 
  through 
  a 
  mass 
  of 
  high 
  hills, 
  then 
  turns 
  

   northwest, 
  and, 
  the 
  mountains 
  falling 
  away 
  on 
  either 
  hand, 
  the 
  river 
  

   sweeps 
  out 
  into 
  the 
  Snake 
  Eiver 
  Plains, 
  in 
  which 
  it 
  joins 
  the 
  Snake 
  

   Eiver. 
  

  

  The 
  Snake 
  Eiver 
  Plains 
  are 
  an 
  enormous 
  field 
  of 
  basalt 
  extending 
  

   westward 
  from 
  about 
  longitude 
  112° 
  nearly 
  to 
  the 
  western 
  boundary 
  of 
  

   Idaho, 
  and 
  from 
  near 
  latitude 
  42° 
  north 
  to 
  the 
  southern 
  base 
  of 
  the 
  

   Bitterroot 
  and 
  Salmon 
  Eiver 
  Eanges. 
  The 
  surface 
  is 
  slightly 
  undu- 
  

   lating 
  and 
  is 
  seamed 
  with 
  crevasses 
  like 
  a 
  field 
  of 
  old 
  ice. 
  Most 
  of 
  the 
  

   streams 
  which 
  enter 
  this 
  region 
  soon 
  disappear 
  beneath 
  its 
  surface, 
  

   perhaps 
  to 
  appear 
  and 
  disappear 
  again. 
  The 
  soil 
  is 
  mainly 
  a 
  shifting 
  

   sand, 
  which, 
  driven 
  by 
  the 
  prevailing 
  westerly 
  winds, 
  has 
  collected 
  in 
  

   dunes 
  on 
  the 
  eastern 
  and 
  northeastern 
  border. 
  This 
  great 
  area 
  is 
  mainly 
  

   covered 
  with 
  sage, 
  which 
  grows 
  luxuriantly, 
  attaining 
  arborescent 
  pro- 
  

   portions. 
  In 
  the 
  interior 
  and 
  southern 
  portions 
  of 
  this 
  waste 
  this 
  mam- 
  

   moth 
  growth 
  of 
  sage 
  is 
  the 
  only 
  product 
  of 
  the 
  soil, 
  but 
  near 
  the 
  base 
  of 
  

   the 
  mountains 
  on 
  the 
  east 
  and 
  north 
  grass 
  gradually 
  takes 
  the 
  place 
  of 
  

   sage, 
  in 
  a 
  measure, 
  and 
  on 
  the 
  lower 
  mountain 
  slopes 
  it 
  monopolizes 
  the 
  

   soil 
  to 
  the 
  practical 
  exclusion 
  of 
  other 
  growths. 
  

  

  The 
  country 
  along 
  the 
  northern 
  margin 
  of 
  these 
  plains, 
  i. 
  e., 
  that 
  lying 
  

   at 
  the 
  base 
  of 
  the 
  Bitterroot 
  and 
  Salmon 
  Eiver 
  Eanges, 
  with 
  the 
  lower 
  

   slopes 
  of 
  these 
  mountains, 
  can 
  easily 
  be 
  burned 
  over. 
  The 
  larger 
  part 
  

   of 
  the 
  area 
  of 
  these 
  plains, 
  however, 
  falls 
  in 
  that 
  debatable 
  ground 
  

   where 
  it 
  is 
  very 
  difficult 
  to 
  decide 
  whether 
  it 
  is 
  or 
  is 
  not 
  burnable, 
  eco- 
  

   nomically. 
  In 
  some 
  localities 
  the 
  Artemisia 
  is 
  so 
  abundant 
  and 
  so 
  luxu- 
  

  

  